Power distribution in transport refrigeration system

ABSTRACT

A transport refrigeration system includes a refrigeration unit including a controller configured to control the refrigeration unit; an electric power device configured to provide power to a refrigeration component of the refrigeration unit; an export power module (EPM) including: an EPM controller in communication with the controller; a power control device configured to receive power from the electric power device; an auxiliary device coupled to the power control device; wherein the controller is configured to communicate with the EPM controller to control power supplied from the electric power device to the auxiliary device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Application No. 62/852,451,filed on May 24, 2019, which is incorporated herein by reference in itsentirety.

BACKGROUND

The subject matter disclosed herein relates generally to transportrefrigeration systems, and more particularly to controlling electricpower distribution in a transport refrigeration system.

Transport refrigeration systems often employ a source of electric powerto power refrigeration components, such as a compressor, fans, heatingcoils, etc. An existing transport refrigeration system uses an enginedriven generator to produce electric power. At times, the transportrefrigeration system does not require all the electric power produced bythe source of electric power.

BRIEF DESCRIPTION

According to one embodiment, a transport refrigeration system includes arefrigeration unit including a controller configured to control therefrigeration unit; an electric power device configured to provide powerto a refrigeration component of the refrigeration unit; an export powermodule (EPM) including: an EPM controller in communication with thecontroller; a power control device configured to receive power from theelectric power device; an auxiliary device coupled to the power controldevice; wherein the controller is configured to communicate with the EPMcontroller to control power supplied from the electric power device tothe auxiliary device.

In addition to one or more of the features described above, or as analternative, further embodiments may include wherein the EPM controlleris configured to determine a power requested by the auxiliary device;the EPM controller is configured to communicate the power requested tothe controller.

In addition to one or more of the features described above, or as analternative, further embodiments may include wherein the controller isconfigured to determine a power available from the refrigeration unit.

In addition to one or more of the features described above, or as analternative, further embodiments may include wherein the controller isconfigured to determine the power available in response to a sensedoutput of the electric power device.

In addition to one or more of the features described above, or as analternative, further embodiments may include wherein the controller isconfigured to determine the power available in response to an operatingmode of the refrigeration unit.

In addition to one or more of the features described above, or as analternative, further embodiments may include wherein the controller isconfigured to compare the power requested to the power available.

In addition to one or more of the features described above, or as analternative, further embodiments may include wherein the controller isconfigured to enable full export of power from the refrigeration unit tothe auxiliary device when the power available exceeds the powerrequested.

In addition to one or more of the features described above, or as analternative, further embodiments may include wherein the controller isconfigured to enable limited export of power from the refrigeration unitto the auxiliary device when the power available does not exceed thepower requested.

In addition to one or more of the features described above, or as analternative, further embodiments may include wherein the power controldevice imposes a current limit on the power provided to the auxiliarydevice.

In addition to one or more of the features described above, or as analternative, further embodiments may include an auxiliary power sourceconfigured to augment power supplied from the electric power device tothe auxiliary device.

According to another embodiment, a method for distributing power in atransport refrigeration system includes generating power at arefrigeration unit; determining a power requested by an auxiliarydevice; determining a power available from the refrigeration unit;comparing the power requested to the power available; distributing powerfrom the refrigeration unit to the auxiliary device in response to thecomparing the power requested to the power available.

In addition to one or more of the features described above, or as analternative, further embodiments may include wherein determining thepower available comprises sensing an output of the refrigeration unit.

In addition to one or more of the features described above, or as analternative; further embodiments may include wherein determining thepower available comprises determining an operating mode of therefrigeration unit.

In addition to one or more of the features described above, or as analternative, further embodiments may include enabling full export ofpower from the refrigeration unit to the auxiliary device when the poweravailable exceeds the power requested.

In addition to one or more of the features described above, or as analternative, further embodiments may include enabling limited export ofpower from the refrigeration unit to the auxiliary device when the poweravailable does not exceed the power requested.

In addition to one or more of the features described above, or as analternative, further embodiments may include imposing a current limit onthe power provided to the auxiliary device.

Technical effects of embodiments include the ability to provide powerdistribution in a transport refrigeration system such that power toauxiliary device(s) is provided in a controlled, metered manner.

BRIEF DESCRIPTION OF HE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 depicts a tractor trailer system in an example embodiment;

FIG. 2 depicts a refrigeration unit in an example embodiment;

FIG. 3 depicts an export power module and auxiliary devices in anexample embodiment;

FIG. 4 depicts a process for distributing electric power in an exampleembodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a tractor trailer system 100 in an example embodiment.The tractor trailer system 100 includes a tractor 102 including anoperator's compartment or cab 104 and an engine, which acts as the drivesystem of the tractor trailer system 100. A trailer 106 is coupled tothe tractor 102. The trailer 106 is a refrigerated trailer 106 andincludes a top wall 108, a directly opposed bottom wall 110, opposedside walls 112, and a front wall 114, with the front wall 114 beingclosest to the tractor 102. The trailer 106 further includes a door ordoors (not shown) at a rear wall 116, opposite the front wall 114. Thewalls of the trailer 106 define a cargo compartment 117. The trailer 106is configured to maintain a cargo 118 located inside the cargocompartment 117 at a selected temperature through the use of a transportrefrigeration system 120 located on or next to the trailer 106. Thetransport refrigeration system 120, as shown in FIG. 1, is located artor attached to the front wall 114. Although the transport refrigerationsystem 120 is depicted as part of a tractor trailer system 100, thetransport refrigeration system 120 may be used with containers having acargo compartment, the containers shippable by land, sea, air, etc.

FIG. 2 depicts a refrigeration unit 20 of the transport refrigerationsystem 120 in an example embodiment. The refrigeration unit 20 includesan electric power device 24 (e.g., a generator), a prime mover 26 (e.g.,a diesel engine) for driving the electric power device 24 and acontroller 30. The refrigeration unit 20 includes a refrigerantcompression device 32, a refrigerant heat rejection heat exchanger 34,an expansion device 36, and a refrigerant heat absorption heat exchanger38 connected in refrigerant flow communication in a closed looprefrigerant circuit and arranged in a conventional refrigeration cycle.The refrigeration unit 20 also includes one or more fans 40 associatedwith the refrigerant heat rejection heat exchanger 34 and driven by fanmotor(s) 42 and one or more fans 44 associated with the refrigerant heatabsorption heat exchanger 38 and driven by fan motor(s) 46. Therefrigeration unit 20 may also include an electric resistance heater 48associated with the refrigerant heat absorption heat exchanger 38. It isto be understood that other components (not shown) may be incorporatedinto the refrigerant circuit as desired, including for example, but notlimited to, a suction modulation valve, a receiver, a filter/dryer, aneconomizer circuit.

The refrigerant heat rejection heat exchanger 34 may, for example,comprise one or more refrigerant conveying coiled tubes or one or moretube banks formed of a plurality of refrigerant conveying tubesextending between respective inlet and outlet manifolds. The fan(s) 40are operative to pass air, typically ambient air, across the tubes ofthe refrigerant heat rejection heat exchanger 34 to cool refrigerantvapor passing through the tubes. The refrigerant heat rejection heatexchanger 34 may operate either as a refrigerant condenser, such as ifthe refrigeration unit 20 is operating in a subcritical refrigerantcycle or as a refrigerant gas cooler, such as if the refrigeration unit20 is operating in a transcritical cycle.

The refrigerant heat absorption heat exchanger 38 may, for example, alsocomprise one or more refrigerant conveying coiled tubes or one or moretube banks formed of a plurality of refrigerant conveying tubesextending between respective inlet and outlet manifolds. The fan(s) 44are operative to pass air drawn from the temperature controlled cargocompartment 117 across the tubes of the refrigerant heat absorption heatexchanger 38 to heat and evaporate refrigerant liquid passing throughthe tubes and cool the air. The air cooled traversing the refrigerantheat absorption heat exchanger 38 is supplied back to the temperaturecontrolled compartment 117. It is to be understood that the term “air”when used herein with reference to the atmosphere within the cargocompartment 117 includes mixtures of air with other gases, such as forexample, but not limited to, nitrogen or carbon dioxide, sometimesintroduced into a refrigerated cargo compartment 117 for transport ofperishable produce.

The refrigerant compression device 32 may comprise a single-stage ormultiple-state compressor such as, for example, a reciprocatingcompressor or a scroll compressor. The compression device 32 has acompression mechanism (not shown) driven by an electric motor 50. In anembodiment, the motor 50 may be disposed internally within thecompressor with a drive shaft interconnected with a shaft of thecompression mechanism, all sealed within a common housing of thecompression device 32.

The controller 30 is configured for controlling operation of therefrigeration unit 20 including, but not limited to, operation ofvarious components of the refrigeration unit 20 to provide and maintaina desired thermal environment within the cargo compartment 117, that iswithin the temperature controlled space in which a perishable product isstowed. The controller 30 may be an electronic controller including amicroprocessor and an associated memory. The controller 30 controlsoperation of various components of the refrigeration unit 20, such asthe refrigerant compression device 32 and its associated drive motor 50,the fan motors 42, 46 and the electric resistance heater 48. Thecontroller 30 may also be able to selectively operate the prime mover26, typically through an electronic engine controller 54 operativelyassociated with the prime mover 26.

The refrigeration unit 20 has a plurality of refrigeration componentsusing electric power, including, but not limited to, the compressiondevice drive motor 50, the drive motor 42 for the fan 40 associated withthe refrigerant heat rejection heat exchanger 34, and the drive motor 46for the fan 44 associated with the refrigerant heat absorption heatexchanger 38. In the depicted embodiment, the electric resistance heater48 also constitutes a power demand load. The electric resistance heater48 may be selectively operated by the controller 30 whenever a controltemperature within the temperature controlled cargo compartment 117drops below a preset lower temperature limit, which may occur in a coldambient environment. In such an event the controller 30 would activatethe electric resistance heater 48 to heat air circulated over theelectric resistance heater 48 by the fan(s) 44 associated with therefrigerant heat absorption heat exchanger 38. The electric resistanceheater 48 may also be used to defrost the refrigerant heat absorptionheat exchanger 38.

The prime mover 26, which comprises an on-board fossil-fuel engine, mostcommonly a diesel engine, drives the electric power device 24 thatgenerates electrical power. The drive shaft of the engine drives theshaft of the electric power device 24. In an electrically poweredembodiment of the transport refrigeration system 120, the electric powerdevice 24 may comprise a single, on-board, engine driven AC generatorconfigured to generate alternating current (AC) power including at leastone AC voltage at one or more frequencies. In an embodiment, theelectric power device 24 may, for example, be a permanent magnet ACgenerator or a synchronous AC generator. In another embodiment, theelectric power device 24 may comprise a single on-board, engine drivenDC generator configured to generate direct current (DC) power at leastone voltage. Some electric generation devices may have internal voltageregulators while other electric generation devices do not. In anotherembodiment, the electric power device 24 does not contain an internalvoltage regulator and thus the voltage of the electric power device 24is unregulated by the electric power device 23 itself. The refrigerationunit 20 has a sensor 28 to sense the voltage and/or current of theelectric power device 24. As each of the fan motors 42, 46 and thecompression device drive motor 50 may be an AC motor or a DC motor, itis to be understood that one or more power converters 52, such as AC toDC rectifiers, DC to AC inverters, AC to AC voltage/frequencyconverters, and DC to DC voltage converters, may be employed inconnection with the electric power device 24 as appropriate.

In other embodiments, the electric power device 24 may include a batterywhich can be charged using regenerative sources brakes of thetractor-trailer, axle mounted generators, solar panels, etc.). The primemover 26 may be eliminated, or used only when the battery charge is at alow level.

FIG. 3 depicts power distribution from the refrigeration unit 20 toauxiliary devices 220 in an example embodiment. At times, the electricpower device 24 provides more power than is needed by the refrigerationunit 20. Excess power may be used by one or more auxiliary devices 220.As shown in FIG. 3, an export power module (EPM) 200 is coupled to theelectric power device 24 to receive power from the electric power device24. Power from the electric power device 24 may pass through the powerconverter(s) 52 prior to supply to the export power module 200. Theexport power module 200 includes an EPM controller 204, The EPMcontroller 204 may be an electronic controller including amicroprocessor and an associated memory. Power from the electric powerdevice 24 is supplied to a switching module 206 for distribution to oneor more auxiliary devices 220. The auxiliary devices 220 may includeelectrically powered devices such as lights in the cargo compartment117, a pallet jack, a lift gate of trailer 106, an air curtain of thetrailer 106, etc. The auxiliary devices 220 in FIG. 3 are examples, andembodiments are not limited to the auxiliary devices 220 depicted inFIG. 3. The auxiliary devices 220 may also connected to an auxiliarypower source 221, such as shore power, a battery, etc.

The switching module 206 includes one or more power control devices 210controlled by the EPM controller 204. The power control devices 210 maybe electro-mechanical (e.g., relays) or electrical (e.g., powertransistors). The power control devices 210 may control an amount ofpower supplied to the auxiliary devices 220 through, for example, avoltage controlled current/voltage regulator. The EPM controller 204 isin communication with the auxiliary devices 220 via a wired and/orwireless interface 224, such as a controller area network (CAN) bus. TheEPM controller 204 is also in communication with the controller 30 via avia a wired and/or wireless interface 226, such as a CAN bus. Theinterfaces 224 and 226 may be implemented using a single interface, suchas a CAN bus.

FIG. 4 depicts a process of controlling power distribution in thetransport refrigeration system 120. The process begins at 300 where theEPM controller 204 determines a power requested by one or more of theauxiliary devices 220. This may be achieved by the EPM controller 204receiving a power request over the interface 224. The power request maybe in the form of a power-on signal from a respective auxiliary device220. The EPM controller 204 may store power requirements for each of theauxiliary devices 220 in memory to determine the power requested.

The EPM controller 204 communicates the power requested to thecontroller 30 over the interface 226. At 302, the controller 30determines a power available from the refrigeration unit 20. Thecontroller 30 may determine the output voltage and/or current from theelectric power device 24 through sensor 28. The controller 30 may alsodetermine the operating mode of the refrigeration unit 20, such aspull-down, steady state, heating, defrost, off, etc. In response to theoutput of the electric power device 24 and/or the operating mode of therefrigeration unit 20, the controller 30 determines the power availablefrom the refrigeration unit 20.

At 304, the controller 30 determines if the power available from therefrigeration unit 20 is greater than or equal to the power requested bythe EPM controller 204. If so, flow proceeds to 306 where the controller30 communicates with the EPM controller 204 to enable full export powerto the auxiliary devices 220. The EPM controller 204 controls the powercontrol devices 210 to provide all available power from therefrigeration unit 20 to one or more of the auxiliary devices 220. Ifadditional power is needed, the auxiliary power source 221 may be usedto augment power from the refrigeration unit 20.

If at 304, the power available from the refrigeration unit 20 is notgreater than or equal to the power requested by the EPM controller 204,flow proceeds to 308. At 308, the controller 30 communicates with theEPM controller 204 to enable limited export power to the auxiliarydevices 220. The controller 30 may send a command to the EPM controller204 indicating a current limit. The EPM controller 204 controls thepower control devices 210 to limit power from the refrigeration unit 20to one or more of the auxiliary devices 220. For example, the EPMcontroller 204 may generate a command voltage to a power control device210, the command voltage imposing a current limit on the power providedto the auxiliary devices 220. If additional power is needed, theauxiliary power source 221 may be used to augment power from therefrigeration unit 20.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

As described herein, in some embodiments various functions or acts maytake place at a given location and/or in connection with the operationof one or more apparatuses, systems, or devices. For example, in someembodiments, a portion of a given function or act may be performed at afirst device or location, and the remainder of the function or act maybe performed at one or more additional devices or locations. Further,one of ordinary skill in the art will appreciate that the stepsdescribed in conjunction with the illustrative figures may be performedin other than the recited order, and that one or more steps illustratedmay be optional.

Those of skill in the art will appreciate that various exampleembodiments are shown and described herein, each having certain featuresin the particular embodiments, but the present disclosure is not thuslimited. Rather, the present disclosure can be modified to incorporateany number of variations, alterations, substitutions, combinations,sub-combinations, or equivalent arrangements not heretofore described,but which are commensurate with the scope of the present disclosure.Additionally, while various embodiments of the present disclosure havebeen described, it is to be understood that aspects of the presentdisclosure may include only some of the described embodiments.Accordingly, the present disclosure is not to be seen as limited by theforegoing description, but is only limited by the scope of the appendedclaims.

What is claimed is:
 1. A transport refrigeration system comprising: arefrigeration unit including: a controller configured to control therefrigeration unit; an electric power device configured to provide powerto a refrigeration component of the refrigeration unit; an export powermodule (EPM) including: an EPM controller in communication with thecontroller; a power control device configured to receive power from theelectric power device; an auxiliary device coupled to the power controldevice; wherein the controller is configured to communicate with the EPMcontroller to control power supplied from the electric power device tothe auxiliary device.
 2. The transport refrigeration system of claim 1wherein: the EPM controller is configured to determine a power requestedby the auxiliary device; the EPM controller is configured to communicatethe power requested to the controller.
 3. The transport refrigerationsystem of claim 2 wherein: the controller is configured to determine apower available from the refrigeration unit.
 4. The transportrefrigeration system of claim 3 wherein: the controller is configured todetermine the power available in response to a sensed output of theelectric power device.
 5. The transport refrigeration system of claim 3wherein: the controller is configured to determine the power availablein response to an operating mode of the refrigeration unit.
 6. Thetransport refrigeration system of claim 3 wherein: the controller isconfigured to compare the power requested to the power available.
 7. Thetransport refrigeration system of claim 6 wherein: the controller isconfigured to enable full export of power from the refrigeration unit tothe auxiliary device when the power available exceeds the powerrequested.
 8. The transport refrigeration system of claim 6 wherein: thecontroller is configured to enable limited export of power from therefrigeration unit to the auxiliary device when the power available doesnot exceed the power requested.
 9. The transport refrigeration system ofclaim 8 wherein: the power control device imposes a current limit on thepower provided to the auxiliary device.
 10. The transport refrigerationsystem of claim 1 further comprising: an auxiliary power sourceconfigured to augment power supplied from the electric power device tothe auxiliary device.
 11. A method for distributing power in a transportrefrigeration system, the method comprising: generating power at arefrigeration unit; determining a power requested by an auxiliarydevice; determining a power available from the refrigeration unit;comparing the power requested to the power available; distributing powerfrom the refrigeration unit to the auxiliary device in response to thecomparing the power requested to the power available.
 12. The method ofclaim 11 wherein: determining the power available comprises sensing anoutput of the refrigeration unit.
 13. The transport refrigeration systemof claim 11 wherein: determining the power available comprisesdetermining an operating mode of the refrigeration unit.
 14. The methodof claim 11 further comprising: enabling full export of power from therefrigeration unit to the auxiliary device when the power availableexceeds the power requested.
 15. The method of claim 11 furthercomprising: enabling limited export of power from the refrigeration unitto the auxiliary device when the power available does not exceed thepower requested.
 16. The method of claim 15 further comprising: imposinga current limit on the power provided to the auxiliary device.